A conventional suspension type bolt drawing machine is suspended through a trolley and a hoist which are disposed above a pressure container to which bolts are attached and can be moved horizontally and vertically. Such a bolt drawing machine is positioned above a predetermined bolt (or stud) and then lowered, and at this time it is necessary to position the bolt drawing machine exactly. A conventional bolt drawing machine approaches a target bolt by repeating visual confirmation and approach, and the trolley is moved to the target position. However, with such a bolt drawing machine and the positioning manner, precise positioning can not be attained. More particularly, in order to lift up and down the bolt drawing machine without collision of the bolt drawing machine to the bolt, the positioning accuracy of .+-. 3 mm or less is required. However, only control of a halt position of the trolley can not obtain such high accuracy. If the bolt drawing machine comes into contact with the bolt when the bolt drawing machine is lifted up and down, accurate and expensive threads of both may be damaged each other.
In the conventional suspension type transporter, there is a case where a hydraulic or pneumatic hose and a cable are hung down from the trolley and coupled with the bolt drawing machine. In this case, when the bolt drawing machine is lifted up and down by the hoist, bending force and weight of the hose and the cable are applied to the bolt drawing machine and the wire suspending the bolt drawing machine is twisted. Accordingly, the bolt drawing machine may not take a preferable position with respect to the bolt. Further, when moving on a traveling path which curves at a certain radius of curvature, the bolt drawing machine is swung outside to cause rolling. When external force produced by an earthquake is further applied, twist and rolling are both produced. In such a situation, when the bolt drawing machine is to be positioned, exact positioning of the bolt drawing machine is not possible due to the twist and rolling.
Further, when the bolt drawing machine is hung down to be transported by the conventional suspension type transporter under control of its controller, the bolt drawing machine tends to be swung forward and backward in the traveling direction. Thus, not only deviation of phase in traveling occurs between the trolley and the bolt drawing machine, but also deviation of moving distance occurs due to extension of the wire. Accordingly, when the position is detected by the trolley, the positioning accuracy of the bolt drawing machine is reduced.
The present invention has been made to improve the above drawbacks.
It is a first object of the present invention to provide a suspension type transporter in which twist and rolling of a wire suspending a bolt drawing machine is prevented to be able to attain accurate positioning.
It is a second object of the present invention to provide a positioning controller for a suspension type transporter which detects deviation of moving distance due to swing of the bolt drawing machine in the traveling direction and extension of a wire to correct the deviation so that the transporter can be positioned with high accuracy.